The BlackBerry mobile phone maker was in talks with the police over whether its handsets are being used by gangs to organise the London riots.

The company's encrypted message system is being used by rioters to decide on potential targets and then advertise their whereabouts, through closed networks, to hundreds of fellow looters.

Detectives have begun sifting through mountains of evidence to try to pin down the ringleaders of London's worst rioting in more than 25 years in an operation that could lead to hundreds of arrests.

Officers will sift through thousands of photographs, web pages and CCTV images taken throughout the disturbances to build up a picture of who is leading the violent outbursts.

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Some of those involved in the riots used websites to post pictures of themselves standing next to looted goods. Evidence suggests that the hardcore organisers are not so foolhardy, opting instead to use the encrypted safety that comes from their BlackBerry phones to communicate with impunity.

Co-operation from the Canadian phone giant Research in Motion, which makes BlackBerry handsets, could prove vital in securing successful prosecutions. Unlike Twitter - which is open to the public and easy for the police to monitor - BlackBerry messaging uses a private network.

BlackBerry messages were sent throughout the weekend calling on looters to target certain areas at specific times. One, which began circulating just hours before rioters descended on Enfield, read: "Everyone in Edmonton, Enfield, Wood Green, everywhere in north link up at Enfield Town station at 4 o'clock sharp. Start leaving ur yards n linking up with your n*****. F*** da feds, bring yourO bags trollys, cars vans, hammers the lot!!"

Another read: "Wanted: nuff n***** and bitches. Tonite nw london gets hit."

Patrick Spence, the managing director of BlackBerry UK, said his technicians were willing to "assist" police investigations. "We feel for those impacted by this weekend's riots in London," he said. "We have engaged with the authorities to assist in any way we can. As in all markets around the world where BlackBerry is available we co-operate with local telecommunications operators, law enforcement and regulatory officials."

But the company refused to elaborate on whether it would be willing to hand over private users' data without a court order, or give police access to the messages. Last year it refused to co-operate with the Governments of Saudi Arabia and the UAE when they sought access to encrypted messages.

For anyone eventually caught and convicted of rioting the penalties are particularly stiff, with courts keen to apply harsh sentences in order to set an example. Under the Public Order Act those found guilty of rioting can face anything up to 10 years in prison.

The lesser charge of violent disorder can carry a sentence of up to five years'. A number of demonstrators involved in the recent student protests have been sentenced to as much as 18 months for violent disorder.

Once the preserve of business leaders, BlackBerries have become increasingly popular among teenagers who are attracted to the cheaper handsets - and the network's virtually free messaging system. A report last week by Ofcom showed that 37 per cent of British teenagers now use BlackBerry handsets.

The Metropolitan Police has also been using its "forward intelligence teams", officers who specialise in photographing and filming troublemakers.

- Independent